Serbian leaders have warned that support for joining the European Union is waning in favor of stronger ties with Russia, the Balkan country's traditional Slavic ally.

Prime Minister Aleksandar Vucic said on October 13 that EU membership remains the goal of his government, despite a changed atmosphere recently which has welcomed a bigger Russian presence in the country.

"In a way, we are losing ground," Vucic said. "We succeeded in losing political momentum and today is a completely different atmosphere...than it used to be a year or two years ago."

In a sign of the change, the Russian and Serbian militaries held a joint air-force drill this week near Belgrade. Serbia has previously assured Russia that it will never join NATO, despite its interest in joining the EU.

Serbia since 2014 has also refused to impose economic sanctions against Russia for its aggression in Ukraine, as EU members have.

Moscow has backed Serbia in its dispute with the West over Kosovo, a predominantly ethnic Albanian former province whose 2008 declaration of independence Serbia has refused to recognize.

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While Vucic spoke in Belgrade, Serbia's pro-Russian President Tomislav Nikolic was visiting Moscow and told TASS that Serbia would never recognize Kosovo to obtain EU membership.

"Serbia will never become an EU member if in exchange it is asked to recognize the independence of Kosovo," he said. "But they do not hear us and keep putting forward this precondition again and again."